Modern highways are typically constructed of end-to-end slabs of unreinforced concrete which are laid over an asphaltic or concrete sub-base. The concrete is laid in slabs, leaving transverse joints which will allow the concrete to expand and contract with seasonal and daily temperature changes. The transverse joints are usually sealed with resilient materials such as oxidized asphalt, rubberized asphalt and preformed neoprene. They are adapted to expand and contract with the concrete and function to prevent the introduction of ground water, sand and other materials into the joint that may interfere with its function.
In addition to longitudinal expansion and contraction, the concrete slabs also curl in conjunction with daily temperature swings. The curling is caused by temperature differences occurring between the top and the bottom of the slab such as occurs each evening after sundown or each morning following sunrise. When the concrete slabs are in a concave configuration (i.e., the ends of the slabs are curled up), a void occurs between the bottom of the slab and the sub-base.
The dimished sub-base support at the joints causes a pumping action when traffic passes over the distorted slabs, and this has the effect of forcing "fines", such as sand, clay, etc., under the ends of the respective slab or slabs. The incompressible fines cause the joint to be fixed in a faulted position, leading to a rough ride for vehicular traffic and eventual cracking at the slab ends. Grinding of the fines under the pavement may also erode the sub-base.
Attempts to solve the faulting problems in highways by pumping materials which harden under the slab have proved ineffective. Conventional sealants are too viscous to fill the void, too hard, or are not flexible enough to follow the movements of the concrete.
It has now been discovered that pumping flowable, curable compositions of a type which cure to resilient and flexible foams solves the problem of repairing damaged highways, and this is a major object of the present invention.
Also, in another aspect of the present invention, before the slabs in new construction have had a chance to distort, the fines can be prevented from entering the areas adjacent the transverse joints by injecting such compositions to form a foamed barrier.